Local Variables

Global Variables

Global variables are those defined outside of any function, making them accessible from anywhere within the script. Regardless of the keyword used for declaration, they all behave similarly and possess a global scope. Even variables declared without a keyword inside a function are considered global....

Local Variables

Local variables are defined within functions in JavaScript. They are confined to the scope of the function that defines them and cannot be accessed from outside. Attempting to access local variables outside their defining function results in an error....

How to use variables

The scope of a variable or function determines what code has access to it.Variables that are created inside a function are local variables, and local variables can only be referred to by the code within the function.Variables created outside of functions are global variables, and the code in all functions has access to all global variables.If you forget to code the var keyword in a variable declaration, the JavaScript engine assumes that the variable is global. This can cause debugging problems.In general, it’s better to pass local variables from one function to another as parameters than it is to use global variables. That will make your code easier to understand with less chance of errors....

Where to use which variable

It’s tempting to resort to global variables for their apparent simplicity, but they often lead to issues. Since any function can modify a global variable, it’s easy to unintentionally alter them or make errors like misspelling variable names, especially in larger applications. Debugging such issues can become cumbersome.In contrast, local variables offer a solution by reducing the risk of naming conflicts. Different functions can use identical names for local variables without causing clashes. This minimizes errors and debugging challenges. Therefore, except for a few specific cases, it’s advisable to encapsulate code within functions to ensure variables remain local.Remember, misspelling a variable name that’s already declared results in a new global variable being created. To prevent this, always declare variables with keywords and ensure they’re declared before use in the code....